• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 II
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• pp.739-744
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• 2001

In order to investigate the stability of magneto-rheological fluid based squeeze film damper (MR-SFD), its negative stiffness effect, which arises from magnetization of MR-SFD, is identified theoretically and experimentally. The analytical model of MR-SFD includes the magnetic circuit as well as the displacement stiffness associated with the squeeze mode of MRF. Extensive experiments are carried out to measure the magnetic attraction forces generated in the MR-SFD, with the excitation frequency and the eccentricity of the journal varied, which are controlled by an active magnetic bearing. The simulation and experimental results are found to be in good agreement. It is concluded that the negative stiffness effect dominates only in the low frequency region because its effect diminishes in the high frequency region due to the eddy-current loss.

• 대한수학회논문집
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• 제13권3호
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• pp.525-538
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• 1998

Recently, a stability theorem for the Feynman integral as a bounded linear operator on$ L_2$($R^{d}$ /) with respect to measures whose positive and negative variations are in the generalized Kato class was proved. We study a stability theorem for the Feynman integral with respect to measures whose positive variations are in the class of $\sigma$-finite smooth measures and negative variations are in the generalized Kato class. This extends the recent result in the sense that the class of $\sigma$-finite smooth measures properly contains the generalized Kato class.

• ETRI Journal
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• 제31권1호
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• pp.62-64
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• 2009

We report on the bias stability characteristics of transparent ZnO thin film transistors (TFTs) under visible light illumination. The transfer curve shows virtually no change under positive gate bias stress with light illumination, while it shows dramatic negative shifts under negative gate bias stress. The major mechanism of the bias stability under visible illumination of our ZnO TFTs is thought to be the charge trapping of photo-generated holes at the gate insulator and/or insulator/channel interface.

• International Journal of Automotive Technology
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• 제8권4호
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• pp.395-402
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• 2007

Homogeneous Charge Compression Ignition (HCCI) shows great potential for low $NO_x$ emission but is hampered by the problem of no direct method to control the combustion process. Therefore, HCCI combustion becomes unstable easily, especially at lower and higher engine load. This paper presents a method to achieve diesel-fueled HCCI combustion, which involves directly injecting diesel fuel into the cylinder before the piston arrives at top dead center in the exhaust stroke and adjusting the valve overlap duration to trap more high temperature residual gas in the cylinder. The combustion stability of diesel-fueled HCCI combustion and the effects of engine load, speed, and valve overlap on it are the main points of investigation. The results show that: diesel-fueled HCCI combustion has two-stage heat release rate (low temperature and high temperature heat release) and very low $NO_x$ emission, combustion stability of the HCCI engine is worse at lower load because of misfire and at higher load because of knock, the increase in engine speed aids combustion stability at lower load because the heat loss is reduced, and increasing negative valve overlap can increase in-cylinder temperature which aids combustion stability at lower load but harms it at higher load.

• The Journal of Asian Finance, Economics and Business
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• 제9권2호
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• pp.1-14
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• 2022

The implications of bank-specific risks and macroeconomic risks on the growth, profitability, and stability of Islamic and conventional banks are examined and compared in this article. The study also investigates whether corporate governance mitigates the effects of both bank-specific and macroeconomic risks on Islamic and conventional banks' development, profitability, and stability. For the period 2007-2019, we examined a panel data set of 22 banks in Pakistan, including both Islamic and conventional banks. We discovered considerable evidence that both bank-specific risks and macroeconomic risks have negative effects on the growth, profitability, and stability of Pakistani banks using a dynamic panel data estimator, the two-step Generalized Method of Moments (GMM) approach. Furthermore, the findings show that bank-specific and macroeconomic risks have different consequences in both types of banking. The impacts of liquidity risk, operational risk, capital risk, inflation risk, and exchange rate risk are higher for Islamic banks than for conventional banks. Conventional banks, on the other hand, are more vulnerable to credit risk and interest rate risk. Finally, the findings show that good corporate governance reduces the negative consequences of both categories of risks on bank development, profitability, and stability. This is true for Islamic and conventional banks alike.

• 한국동물위생학회지
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• 제36권4호
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• pp.255-261
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• 2013

The objective of the present study was to determine the minimum alcohol (ethanol) concentration that gives rise to the coagulation of goat milk for the alcohol precipitation test, and to evaluate the physical parameters of goat milk which include alcohol and heat stability. A total of 1,295 udder-half milk samples from 648 lactating dairy goats were collected from seven farms in Jeonnam province, Republic of Korea, to determine the alcohol and heat stability. The majority (99.6%) of the samples were coagulated when 70% ethanol was added to the milk, while only 11.0% of the samples were precipitated by the addition of an equal volume of 45% ethanol. With the concentration of 65%, 60%, 55% and 50% aqueous ethanol, 99.2%, 96.8%, 81.0% and 52.8% of the milk samples were coagulated, respectively. Of 1,295 dairy goat milk samples tested for heat stability, 127 (9.8%) were coagulated by boiling. Among the 143 alcohol test-positive udder-half milk samples, 52 (4.0%) were unstable by heat test, while 1,032 (79.7%) of the 1,152 alcohol test-negative milk samples were stable by heat test. According to the results of boiling test, sensitivity and specificity of 45% alcohol precipitation test were 0.3023 (95% CI: 0.2346~0.3772) and 0.9190 (95% CI: 0.9017~0.9344), respectively. The contents of protein and the specific gravity were higher in the milk samples of 45% alcohol test-positive than in those of 45% alcohol test-negative. However, lower levels of lactose and milk urea nitrogen were observed in the milk samples of 45% alcohol test-positive compared to the alcohol test-negative milk samples. The lowest pH values ($6.73{\pm}0.20$) were shown in the 45% alcohol test-negative and heat-unstable milk samples, while the lowest values of somatic cell counts and bacterial counts were shown in the 45% alcohol test-negative and heat-stable milk samples. Results of this study suggest that the alcohol precipitation for dairy goat milk may have to be tested with ethanol concentration less than 45% for the determination of freshness and heat-stability.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2007년 가을학술발표회
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• pp.481-501
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• 2007

Excessive rainfalls due to climatic changes can trigger an increase in rainfall-induced slope failures that pose real threats to both lives and properties. Many high slopes in residual soils could stand at a steep angle, but failed during or after rainfall. Commonly, these slopes have a deep groundwater table and negative pore-water pressures in the unsaturated zone above the groundwater table contribute to the shear strength of soil and consequently to factor of safety of the slope. Stability assessment of slope under rainfall requires information on rate of rainwater infiltration in the unsaturated zone and the resulting changes in pore-water pressure and shear strength of soil. This paper describes the application of unsaturated soil mechanics principles and theories in the assessment of rainfall effect on stability of slope through proper characterization of soil properties, measurement of negative pore-water pressures, seepage and slope stability analyses involving unsaturated and saturated soils. Factors controlling the rate of changes in factor of safety during rainfall and a preventive method to minimize infiltration are highlighted in this paper.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2016년도 춘계학술대회
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• pp.108-109
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• 2016

선박이 횡경사 되었을 때, 그 발생 원인을 파악하고 적절히 대응하는 것은 매우 중요하다. 특히 최근 발생한 대형 해난사고 중 일부는 항행중 복원력 감소에 의한 횡경사와 관련된 것으로 추정된다. 본 연구에서는 음의 복원력(-GM)에 의한 선박의 횡경사를 실험하고, 그 값을 동일 조건에서의 계산값과 비교하였다. 또한 Loll과 List를 구별하는 것과 Loll 발생 시 대응방안에 대해서 기술하고자 한다.

• 전기의세계
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• 제16권2호
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• pp.17-21
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• 1967

In reactor operation, it is widely known that the absolute stability may not exist for multiple feedback paths even though the single lumped negative temperature coefficient feedback case is clearly stable at all frequencies above those creating xenon poisoning effects. However, interesting and useful stability information may be obtained from a two-path temperature coefficient feedback which can be represented in a water-cooled, water-moderated hetergeneous reactor. In this paper, the outline of an operating stability of a reactor having two-path temperature coefficient feedback is analyzed and described neglecting poison effects.

• 한국전기전자재료학회논문지
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• 제30권1호
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• pp.59-62
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• 2017

CNT (carbon nanotube) resistors with low resistance and negative TCR (temperature coefficient of resistance) were fabricated with yarned CNT (carbon nanotube) fibers. The CNT fibers were prepared by yarning CNTs grown on the silicone substrate by CVD (chemical vapor deposition) method. The CNT resistors were fabricated by winding CNT fibers on the surface of ceramic rod. Both metal terminals were connected with the CNT fiber wound on the ceramic rod. We measured electrical resistance and thermal stability with the number of CNT fibers wound. The CNT resistor system shows linearly decreased resistance with the number of CNTs wound on the ceramic rod and saturated at 20 strands. The CNT resistor system has negative TCR between $-1,000{\sim}-2,000ppm/^{\circ}C$ and stable frequency properties under 100 kHz.